Before I purchased I was shopping around and I noticed most mulching kits for other mowers came with a different blade. But the kit they recommend for this mower (42-in mulch kit (228462)) is only a plastic cover. Is that really all I need to make this a mulching mower? The same blade it came with is fine for mulching?

That is a very good question. I wish your dealer was more helpful with your options. If I had to guess, it seems you can use the mulching "cover" with your existing 3-in-1 blades or you can install the full mulch kit with the plastic baffle and dedicated mulching blades.

Common sense tells me the baffles and dedicated blades would probably work better but I have no experience with either on a D110.

I have the baffles and dedicated mulching blades on my X500 w/48" deck and am extremely happy with the way it cuts and mulches.

Registered

...Before I purchased I was shopping around and I noticed most mulching kits for other mowers came with a different blade. But the kit they recommend for this mower (42-in mulch kit (228462)) is only a plastic cover. Is that really all I need to make this a mulching mower? The same blade it came with is fine for mulching?

That doesn't sound right. My X350 mulch kit came with different blades -- the dealer gave the original blades back to me. Any blades will "work" but a mulching blade provides lift to allow time for more cuts, meaning smaller pieces. You should talk with a dealer, not a reseller.